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SSDs: The New King of the Data Center?
Nerval's Lobster writes "Flash storage is more common on mobile devices than data-center hardware, but that could soon change. The industry has seen increasing sales of solid-state drives (SSDs) as a replacement for traditional hard drives, according to IHS iSuppli Research. Nearly all of these have been sold for ultrabooks, laptops and other mobile devices that can benefit from a combination of low energy use and high-powered performance. Despite that, businesses have lagged the consumer market in adoption of SSDs, largely due to the format's comparatively small size, high cost and the concerns of datacenter managers about long-term stability and comparatively high failure rates. But that's changing quickly, according to market researchers IDC and Gartner: Datacenter- and enterprise-storage managers are buying SSDs in greater numbers for both server-attached storage and mainstream storage infrastructure, according to studies both research firms published in April. That doesn't mean SSDs will oust hard drives and replace them directly in existing systems, but it does raise a question: are SSDs mature enough (and cheap enough) to support business-sized workloads? Or are they still best suited for laptops and mobile devices?"
TL/DR: "The relative cost of the two configurations shows that over-all there are cost savings using the SSD instances"
at least for their use-case (Cassandra).
At work we also use SSDs for a couple terabyte Lucene index with great success (and far cheaper than getting a couple TB of DRAM spread across the servers instead)
You have to remember that enterprise level storage isn't a single set of drives holding the data, it's a hierarchy of different technologies depending upon the speed of data access required. Since SSDs arrived they've been used at the highest access rate end of the spectrum, essentially using their low latency for caching filesystem metadata. I can see that now they are starting to replace the small, high speed drives at the front end entirely. However, it's going to be some time before they can even begin to replace the storage in the second tier and certainly not in the third tier storage where access time isn't an issue but reliable, "cheap" and large drives are required. Of course, beyond this tier you generally get on to massive robotic tape libraries anyway, so SSDs will never in the foreseeable future trickle down to here.
Agrajag: "Oh no, not again!"
The enterprise class SSDs are not the same as the "consumer" ones: http://www.anandtech.com/print/6433/intel-ssd-dc-s3700-200gb-review
Don't be surprised if you stick a "consumer" grade one to a heavily loaded DB server and it dies a few months later.
Fine for random read-only loads.
And some consumer grade SSDs aren't even consumer grade (I'm looking at you OCZ: http://www.behardware.com/articles/881-7/components-returns-rates-7.html ).
I think that the wide range adoption of server SSDs also shows how far server installations have progressed toward eliminating all single points of failure.
In the passt HA and 'five nines' was something only done by a few niches, like telephony provider switches or banking big iron. Today it is common in many cloud installations and most sizeable server setups. A single component failing will not stop your service.
If your business can support the extra cost for the SSDs, a failing drive will not stop you and the performance of the service will see great improvements anyway. The power savings may even make the SSD not so costly after all.
We've been using SSDs in our servers since late 2008, starting with Fusion-io ioDrives and Intel drives since then - X25-E and X25-M, then 320, 520 and 710, and now planning to deploy a stack of S3700 and S3500 drives. Our main cluster of 10 servers has 24 SSDs each, we have another 40 drives on a dedicated search server, and smaller numbers elsewhere.
What we've found:
* Read performance is consistently brilliant. There's simply no going back.
* Random write performance on the 710 series is not great (compared to the SLC-based X25-E or ioDrives), and sustained random write performance on the mainstream drives isn't great either, but a single drive can still outperform a RAID-10 array of 15k rpm disks. The S3700 looks much better, but we haven't deployed them yet.
* SSDs can and do die without warning. One moment 100% good, next moment completely non-functional. Always use RAID if you love your data. (1, 10, 5, or 6, depending on your application.)
* Unlike disks, RAID-5 or 50 works pretty well for database workloads.
* We have noted the leading edge of the bathtub curve (infant mortality), but so far, no trailing edge as older drives start to wear out. Once in place, they just keep humming along.
* That said, we do match drives to workloads - SLC or enterprise MLC for random write loads (InnoDB, MongoDB) and MLC for sequential write/random read loads (TokuDB, CouchDB, Cassandra).
This is being driven primarily by increasing levels of virtualisation, which turns everything into a largely random-write disk load, pretty much the worst case scenario for regular old hard disks.